Electromagnetic Induction Essay Research Paper The phenomenon

Electromagnetic Induction Essay, Research Paper

The phenomenon called electromagnetic induction was first noticed and investigated by Michael Faraday, in 1831. Electromagnetic induction is the production of an electromotive force (emf) in a conductor as a result of a changing magnetic field about the conductor and is a very important concept. Faraday discovered that, whenever the magnetic field about an electromagnet was made to grow and collapse by closing and opening the electric circuit of which it was a part, an electric current could be detected in a separate conductor nearby. Faraday also investigated the possibility that a current could be produced by a magnetic field being placed near a coiled wire. Just placing the magnet near the wire could not produce a current. Faraday discovered that a current could be produced in this situation only if the magnet had some velocity. The magnet could be moved in either a positive or negative direction but had to be in motion to produce any current in the wire. The current in the coil is called an induced current, because the current is brought about (or .induced.) by a changing magnetic field (Cutnell and Johnson 705). The induced current is sustained by an emf. Since a source of emf is always needed to produce a current, the coil itself behaves as if it were a source of emf. The emf is known as an induced emf. Thus, a changing magnetic field induces an emf in the coil, and the emf leads to an induced current (705). He also found that moving a conductor near a stationary permanent magnet caused a current to flow in the wire as long as it was moving as in the magnet and coiled wire set-up. Faraday visualized a magnetic field as composed of many lines of induction, along which a small magnetic compass would point. The aggregate of the lines intersecting a given area is called the magnetic flux. Faraday attributed the electrical effects to a changing magnetic flux.

The necessity of motion to produce a current is due to the fact that electromagnetic induction involves a time-varying magnetic field. The same effects can be produced by moving the coil toward and away from a motionless magnetic source. In either case, the key to producing the current is certainly the motion of the magnet or the wire. The magnetic lines of the magnetic field must pass through a loop of the coiled wire. The value of the magnetic flux is proportional to the total number of lines passing through the loop (Serway and Faughn 653). The magnetic flux can be stated in an equation equal to the flux: f = (B)(A) or f = (B)(A) cos q. The value for the magnetic field (B) is multiplied by the area of one loop of the wire coil (A) and the angle at which the magnetic field crosses the plane of the loop. This conclusion lead to the development of other law involving electromagnetic flux.

Sometime after Faraday.s experiments and conclusions, Scottish physicist James Clerk Maxwell proposed that the fundamental effect of changing magnetic flux was the production of an electric field, not only in a conductor, where it could drive an electric charge, but also in space even in the absence of electric charges. Maxwell formulated the mathematical expression relating the change in magnetic flux to the induced electromotive force (emf). This relationship, known as Faraday’s law of induction, states that the magnitude of the emf induced in a circuit is proportional to the rate of change of the magnetic flux that cuts across the circuit. The induced emf along any moving or fixed mathematical path in a constant or changing magnetic field equals the rate at which magnetic flux sweeps across the path (Ohanian 784). The subsequent magnetic field produced in the coil will be in the opposite direction of the magnetic field of the bar magnet. This due to the relationships between the emf, the current, and the magnetic field. If the field were produced in the direction of the magnet.s magnetic field, the system would continue to build in charge due to the effects of an increase in the electromagnetic flux acting on the coil. The system would result in disaster if continued in that manner. The field must, by law, resist the increase of the magnetic flux acting on the coil in order to maintain the balance of the system. The equation for this is: E = – N (qf / qt) where N is the number of loops in the coiled wire and t is the time in which the flux, f, is changed.

This experiment will explore a few of the situations in which a current can be induced by a magnetic field. These have proven useful for the possibilities of producing a current with magnetism. The translation of this is that through construction of generators, the magnetic field passing through the coiled wire produces a useful source of electricity. The induced current and induced emf relate to the amperage and voltage passing through many of our homes today. These discoveries were used to revolutionize the way we lived at the turn of the century by providing the physical laws needed by inventors to produce new technology.

Procedure:

I.Currents Induced in Straight Wires:

1.Connect the single wire apparatus to the power supply as shown. The ammeter should be on high scale. Place one of the small silver compasses on the back ledge. Rotate the ledge and plot the magnetic field. Remember that the magnetic field always runs from north to south. Therefore always put the arrow on your fiel